Currently, sound may be reduced or prevented from reaching a listener in one of two ways. First, a physical barrier, such as a wall, may be placed between the source of the sound and the listener. The wall will absorb some of the sound energy and reflect most of the rest of it. Second, sound waves at the listener's location may be negated by noise cancellation techniques. Noise cancellation relies on a separate audio source that creates a sound wave that is 180° out of phase with the sound to be canceled. However, unless the separate audio source is in exactly the same location and has the same characteristics as the sound source to be cancelled, the sound cancellation will only apply at specific points in space (nodes), not large regions. At other locations where sound waves from the sound source and cancelling source combine and form antinodes, the sound will be amplified.